JP5464417B2 - Wireless activity sensor terminal and sensor network system - Google Patents

Description

  The present invention relates to a technique that can be suitably used for monitoring the health of an animal population by being attached to an animal such as livestock, and more particularly to a wireless sensor terminal and a sensor network system using the same.

  With the advent of cattle BSE several years ago and the epidemic of bird flu, the need to monitor the health of livestock and wild animals has been raised, but recently swine flu It seems that the interest is growing more and more as a result of the human epidemic and the worldwide epidemic.

  In general, the number of livestock kept in breeding houses such as pig houses and poultry houses is very large. Of course, for example, the number of animals inhabiting within the management area is very large. Therefore, it is practically difficult to manually examine animals one by one (one by one). Therefore, for example, as described in Japanese Patent Application Laid-Open No. 2007-306804, a proposal has been made to attach a sensor terminal to livestock and collect and analyze data wirelessly.

  The sensor terminal used for this purpose must be able to continuously sense information on the health status of animals and transmit the obtained information wirelessly. However, since many terminals are attached to many animals, if the frequency of battery replacement increases, the burden of maintenance and replacement work will become excessive, and as a result, it will be necessary to give up to continue management. I could invite you. Therefore, the sensor used for animal health management must be able to operate for a long period of time without requiring battery replacement.

  On the other hand, in order to prevent the animal from feeling as much stress as possible even when the sensor terminal is attached, the sensor terminal is desirably as small and light as possible. In addition, as the number of animals to be monitored increases, a larger number of sensors are required. Therefore, it is desirable to keep the sensor price as low as possible.

JP 2007-306804 A

  As described above, a sensor terminal for health management of an animal group can be manufactured in a small size, light weight and low cost, and can perform information sensing and wireless transmission for a long period of time without battery replacement. This is a very difficult requirement that is desirable.

  The present invention has been made in order to develop a technology that can be a solution to at least one of these requirements.

  One of the novel configurations disclosed in the present specification includes a piezoelectric element, a capacitor connected to the piezoelectric element via an AC / DC conversion circuit, and a CMOS logic inversion circuit whose input unit is connected to the capacitor. It is characterized by providing.

  As is well known, the piezoelectric body of a piezoelectric element has the property of generating a voltage when subjected to deformation. Therefore, by connecting the capacitor to the piezoelectric element via the AC / DC conversion circuit, it is possible to accumulate electric charge in the capacitor by the electromotive force of the piezoelectric element. When the voltage between the capacitors exceeds the threshold voltage of the CMOS logic inversion circuit due to the accumulation of electric charge, the voltage at the output terminal of the CMOS logic inversion circuit changes. Therefore, the above configuration can be used as a sensor by utilizing this voltage change. In addition, the power storage to the capacitor is performed without requiring any external power supply, and the operation of the CMOS logic inversion circuit consumes little power, so this configuration is extremely excellent in power saving.

  The wireless sensor terminal disclosed in this specification includes a wireless transmission circuit configured to perform signal transmission triggered by a change in the output voltage of the CMOS logic inversion circuit.

  According to this configuration, it is not necessary to operate the wireless transmission circuit until a predetermined charge is accumulated in the capacitor and the voltage between the electrodes exceeds the threshold voltage of the CMOS logic inversion circuit. Therefore, the power consumption related to the wireless transmission circuit is very small. In a configuration that is commonly seen, the clock of the wireless terminal must be at least operated, but according to the above configuration, the event that the circuit is operated only when there is a change in the output voltage of the CMOS logic inversion circuit. Because of the driven configuration, power consumption can be significantly reduced.

  That is, according to the above configuration, a wireless sensor terminal that is extremely excellent in power saving can be realized by a sensor circuit that can operate without power and an event-driven transmission circuit.

The acceleration generated by the movement of the living body gives an inertial force to the mass body inside the sensor.
When this inertial force is applied to the piezoelectric body, an electromotive force proportional to the inertial force is induced.
This electromotive force is charged into the electrostatic capacity of the piezoelectric body, generating a voltage.
This voltage is proportional to the acceleration.
This is the principle of the piezoelectric acceleration sensor.

On the other hand, the activity amount sensor (= may be called calorie consumption sensor, kinetic energy sensor, vibration power generation) is as follows.
The acceleration generated by the movement of the living body gives an inertial force to the mass body inside the sensor.
When this inertial force is applied to the piezoelectric body, an electromotive force proportional to the inertial force is induced.
This electromotive force is converted into a direct current and accumulated (= integrated) in a separately provided capacitance.
This action is the accumulation of generated power.
The square of the potential difference between both ends of the accumulated capacitance is proportional to the accumulated power.
Therefore, the square of the potential difference between both ends is proportional to the amount of biological activity.

  Since this sensor measures the electromotive force, it is proportional to the product of acceleration and amplitude of the measurement object, that is, the energy consumption of the measurement object. Therefore, it can be a momentum or activity sensor instead of a conventional acceleration sensor. For example, when the measurement object is a human or an animal, it is possible to identify the calorie consumption.

  Although various sensors can be mounted on the wireless sensor terminal depending on the application, for example, a temperature sensor can be mounted. The temperature is useful information for determining the health state of the living body.

  However, this temperature information can also be used for other applications. In general, the power consumption of a CMOS logic inversion circuit has an excellent feature that it is almost zero. However, the threshold value of the CMOS logic inversion circuit has a temperature characteristic and causes a measurement error due to a temperature change. This error can be corrected if the temperature is known. Therefore, if the temperature data is included in the transmission data of the wireless sensor terminal, the change in the threshold value of the CMOS logic inversion circuit can be obtained by calculation on the receiver side, and the error can be corrected. Therefore, the temperature sensor is one of the preferable sensors to be mounted on the wireless sensor terminal. The receiver is also preferably configured so that the above error correction can be performed based on temperature information.

  Since the wireless sensor terminal performs transmission every time a predetermined charge is accumulated in the capacitor, the transmission frequency is the integral of vibration applied to the sensor unit, that is, the measurement object on which the wireless sensor terminal is mounted. The amount of activity (exercise) is reflected. Therefore, for example, a new type of wireless sensor terminal whose transmission frequency changes reflecting the amount of activity is provided.

  Alternatively, it can be said that a new type of measurement method has been realized that measures the amount of activity of a living body based on the frequency of reception of signals from a sensor terminal. From this point of view, the present specification also discloses a method of operating an apparatus for creating information related to an activity amount of an active object. The method includes receiving a signal transmitted from a wireless sensor terminal, wherein the wireless sensor terminal is a terminal that emits a wireless signal each time an accumulated amount of energy generated by vibration reaches a predetermined value. And configuring information related to an activity amount of an active object to which the wireless sensor terminal is attached based on the number of receptions per unit time of a signal emitted from the wireless sensor terminal.

  As described above, the present invention has been made to develop a technique suitable for the health management of animal populations. However, the developed invention is not limited to the purpose of health management of animal populations, but can be applied to various fields. Is possible.

  Further technical problems, new configurations, and new effects will be described below with reference to the accompanying drawings and model examples.

It is a figure for demonstrating the outline | summary of the sensor network system 100 illustrated by this specification. 1 is a diagram for explaining an overview of a wireless sensor terminal 102 that is a component of a sensor network system 100. FIG. 4 is a diagram for explaining an example of a circuit configuration of a vibration sensor 202 that is a component of the wireless sensor terminal 102. FIG. 4 is a diagram for explaining an example of a circuit configuration of a vibration sensor 202 that is a component of the wireless sensor terminal 102. FIG. 4 is a diagram for describing an example of a circuit configuration of a transmitter 204 that is a component of the wireless sensor terminal 102. FIG. 5 is a flowchart summarizing the operation of a transmitter 204. 2 is a diagram for explaining an overview of a receiving device 104 that is a component of the sensor network system 100. 6 is a diagram for describing one aspect of a reception operation of the reception device 104. FIG. It is a figure for demonstrating an example of the data format of the signal which the wireless sensor terminal transmits. 6 is a diagram for explaining another aspect of the reception operation of the reception device 104. FIG.

  FIG. 1 is a diagram for explaining an outline of a sensor network system 100 described in detail below. The sensor network system 100 includes a plurality of wireless sensor terminals 102 and at least one receiving device 104. Various sensors are incorporated in the wireless sensor terminal 102 and configured to transmit measured data to the receiving device 104 using the wireless medium 106. Such a sensor network system is widely used for remote monitoring of various facilities, but can also be used for remote monitoring of organisms. An example of an animal health management system using a sensor network system is described in Japanese Patent Application Laid-Open No. 2007-306804. As will be described below, the sensor network system 100 introduced herein is also particularly suitably designed for monitoring livestock and the like. Of course, the field of application of the sensor network system 100 is not limited to animal monitoring.

  The wireless sensor terminal 102 is preferably configured to be small and lightweight so that a human or animal can be worn for a long time without any discomfort. More preferably, it is preferable to reduce the size and weight so that it can be attached to a small bird such as a chicken. In addition, when a large number of individuals are equipped with the wireless sensor terminals 102, it is more convenient for the administrator to reduce the work amount as the frequency of battery replacement is smaller. Therefore, it is desirable that the power consumption be as small as possible. As described below, the wireless sensor terminal 102 is devised in various ways to reduce power consumption as much as possible.

  At least one receiving device 104 is provided in the sensor network system 100 and receives data from a plurality of wireless sensor terminals 102. The receiving device 104 can be a computer device that can analyze received data alone, and depending on the embodiment, the analysis result is displayed on a built-in or external display, printed on a printer, a USB memory, It can be configured to output to a removable medium such as a CD-R or to transmit to an external computer through various interfaces. In another embodiment, the receiving device 104 may be a device that transmits the received data to another computer without analyzing (or performing some analysis). Therefore, the receiving device 104 may be connected to the computer network system by wire or wireless.

  FIG. 2 is a diagram for explaining an outline of the configuration of the wireless sensor terminal 102. The wireless sensor terminal 102 includes a vibration sensor 202, a transmitter 204, an antenna 206 for radiating a transmission signal formed by the transmitter 204, a battery 208 for supplying power to each element of the wireless sensor terminal 102, and the like. ing. The vibration sensor 202 has a novel configuration disclosed for the first time in the present specification, and is configured so that the voltage at the voltage detection terminal changes when a certain amount of vibration is accumulated, as will be described later. . The vibration sensor 202 and the transmitter 204 are connected via a voltage detection line 212 so that the transmitter 204 can detect this voltage change. Further, as will be described later, the vibration sensor 202 operates with almost no power and also has a power generation function. Therefore, the vibration sensor 202 and the transmitter 204 are also connected via the power supply line 214 so that the transmitter 204 can use the generated power.

  Depending on the embodiment, in addition to the vibration sensor 202, various sensors can be mounted on the wireless sensor terminal 102 as required. Of course, in some embodiments, sensors other than the vibration sensor 202 may not be mounted. In the embodiment introduced here, a temperature sensor 220 is mounted on the wireless sensor terminal 102 as shown.

  FIG. 3A is a diagram for explaining a circuit configuration for vibration detection in the vibration sensor 202. The vibration sensor 202 has a piezoelectric element 302. As is well known, a piezoelectric body has the property of generating a voltage when a force is applied, and the piezoelectric element can be configured to capture the force as an electrical signal using this property. Element. One of the simplest structures of a piezoelectric element is a structure in which a piezoelectric plate is sandwiched between two electrodes. The piezoelectric element preferably has a shape that is easily deformed by vibration. For example, in a well-known structure, for example, one end of an elongated piezoelectric plate having a conductive film formed on both sides is fixed, Some are cantilevered. The piezoelectric element having such a shape can be formed very small using a known MEMS manufacturing process. Since various structures are known for the piezoelectric element, an appropriate structure can be selected as necessary. Since the piezoelectric element can generate a voltage without applying electric power from the outside, that is, it generates a voltage with zero power consumption, the adoption of the piezoelectric element greatly contributes to the power saving performance of the vibration sensor 202.

  The piezoelectric element 302 is connected in parallel to the capacitor 308 via an AC / DC conversion circuit including diodes 304 and 306. Further, the input portion of the CMOS logic inverting circuit 310 is connected to one electrode side of the capacitor 308.

  Since the voltage generated in the piezoelectric element 302 in response to the vibration inverts the polarity in accordance with the direction in which the piezoelectric element 302 is deformed, it must be alternating. That is, the current generated by the piezoelectric element 302 is an alternating current, but the current is allowed to flow only in a certain direction by the diodes 304 and 306. Therefore, as the piezoelectric element 302 is vibrated, the capacitor 308 is gradually charged. Accumulated. Therefore, if a voltage is applied to the CMOS logic inversion circuit 310 in advance, when the charge accumulated in the capacitor 308 exceeds a certain amount, the input voltage to the CMOS logic inversion circuit 310 exceeds the threshold, and the CMOS logic inversion circuit. The voltage of the output unit 312 of 310 changes (inverts). That is, it can be known that a certain amount of vibration has occurred in the piezoelectric element 302 due to this change in voltage.

  In addition to the illustrated rectifier circuit including the diodes 304 and 306, various rectifier circuits, such as a diode bridge using four diodes, are known, and these may be used instead of the illustrated configuration. Needless to say.

  Since the voltage of the output unit 312 of the CMOS logic inversion circuit 310 does not change until a predetermined amount of electric charge is accumulated in the capacitor 308, the vibration sensor 202 can be said to be an integral type sensor. In addition, although it is necessary to apply a voltage to the CMOS logic inversion circuit 310 in advance, power consumption does not occur only by applying the voltage, and inversion of the output voltage itself in principle also requires power. Since it is not necessary, the vibration sensor 202 consumes little power. Actually, Joule heat is generated in the circuit due to the influence of the current that flows when the output voltage is inverted, and thus power is consumed there, but the influence is insignificant. In a computer processor or the like in which voltage switching is performed at a frequency of several hundred megahertz, the influence of Joule heat is significant, but the vibration sensor 202 is at most on the order of 10 Hz, so the influence is very small. Therefore, the sensor circuit of FIG. 3A is a sensor circuit with extremely low power consumption and extremely excellent power saving performance.

  In addition, since electric charge is accumulated in the capacitor 308, the vibration sensor 202 also provides a function as a generator by effectively using the electric charge. An example of a circuit for using the charge accumulated in the capacitor 308 is shown in FIG. 3B. In FIG. 3B, the same elements as those of the circuit shown in FIG. A major difference from the circuit shown in FIG. 3A is that a capacitor 328 is connected in parallel to the capacitor 308 via a switch 326. By turning on the switch 326, the charge accumulated in the capacitor 308 can be transferred to the capacitor 328. Therefore, the capacitance of the capacitor 328 is preferably much larger than the capacitance of the capacitor 308.

  In order to control opening and closing of the switch 326, a p-channel MOSFET is used as the switch 326, a monostable multivibrator 324 is connected to the p-channel MOSFET, and another CMOS logic inversion circuit 322 is connected in series to the CMOS logic inversion circuit 310. And its output is connected to a monostable multivibrator 324. According to this configuration, when the voltage between the capacitors 308 exceeds the threshold voltage of the CMOS logic inversion circuit 310, the output voltage of the CMOS logic inversion circuit 310 changes from High to Low, and the CMOS logic inversion accordingly. The voltage of the output terminal 323 of the circuit 322 changes from Low to High. The monostable multivibrator 324 is configured to output one pulse in response to this voltage change. This pulse turns on the switch 326 by the p-channel MOSFET for a predetermined time, and the charge is transferred from the capacitor 308 to the capacitor 328.

  Further, by transferring the charge from the capacitor 308 to the capacitor 328, the charge of the capacitor 308 is cleared, and the output voltages of the CMOS logic inversion circuits 310 and 322 are also restored. As a result, the vibration sensor 202 can start to store the newly applied vibration again in the form of charge accumulation in the capacitor 308.

  The power supply line 214 depicted in FIG. 2 is connected to a terminal 327 provided between the switch 326 and the capacitor 328. Through this terminal 327, the transmitter 204 in FIG. 2 can use the electric charge accumulated in the capacitor 328. Note that the voltage detection line 212 depicted in FIG. 2 is connected to a terminal 323 provided at a position reflecting the output voltage of the CMOS logic inversion circuit 322. Therefore, the transmitter 204 can use the voltage change of the voltage of the terminal 323 as a signal transmission trigger.

  As is apparent from the above description, the vibration sensor 202 not only provides information indicating that vibration has occurred while consuming little electric power, but also has a function as a generator that can supply electric power to the outside. Therefore, it can be said that the sensor is extremely excellent in power saving. Also, the circuits and elements described so far can be easily and very small made using known MEMS and semiconductor manufacturing processes. Because of these advantages, the vibration sensor 202 is very suitable for an application to be incorporated in a wireless sensor terminal, which is extremely demanding for small size, light weight and low power consumption.

  Next, the circuit configuration of the transmitter 204 depicted in FIG. 2 will be described with reference to FIG. The transmitter 204 includes a CPU 402 for controlling the operation of the transmitter 204, a memory 404 for storing a program for operating the CPU 402, a transmission circuit 406 for forming a transmission signal, and a terminal for detecting a voltage change of the vibration sensor 202. 408, an antenna output terminal 410, and the like. As illustrated in FIG. 2, when the wireless sensor terminal 102 includes the temperature sensor 220, the transmitter 204 also includes a connection terminal 420 with the temperature sensor 220.

  The program stored in the memory 404 is configured to operate the CPU 402 so as to periodically check the voltage at the terminal 408. The terminal 408 is connected to the output terminal 323 of the CMOS logic inversion circuit 322 (see FIG. 3B) via the voltage detection line 212 (see FIG. 2). When the program stored in the memory 404 detects that the voltage at the terminal 408 has changed from Low to High, the CPU 402 controls the CPU 402 to form data for transmission, and the transmission circuit 406 transmits the data. Configured to do. That is, the transmitter 204 in this embodiment is configured to transmit a signal each time the charge accumulated in the capacitor 308 of the vibration sensor 202 exceeds the threshold voltage of the CMOS logic inversion circuit 310.

  Note that the transmission of the transmission circuit 406 may be triggered by using an interrupt circuit based on a CMOS input in which an interrupt is generated by a voltage change at the terminal 408 without using a check by the CPU. According to such a configuration using a CMOS input interrupt circuit, power is not required for voltage monitoring, so that power consumption of the terminal can be further reduced.

  A certain amount of vibration needs to be applied to the piezoelectric element 302 in order for the charge to be accumulated after the charge of the capacitor 308 is cleared and before the threshold voltage of the CMOS logic inversion circuit 310 is exceeded again. For this reason, when the acceleration of the applied vibration is low, it takes a relatively long time for the charge exceeding the threshold value to be accumulated in the capacitor 308. When the acceleration of the vibration is high, the charge is stored in the capacitor 308. The time until accumulation is relatively short. Then, when the acceleration of vibration is low, the interval of signal transmission by the transmitter 204 is short, and when the acceleration of vibration is high, the interval is long.

  Therefore, the interval of signal transmission by the transmitter 204 is considered to include information related to the integration of vibration applied to the piezoelectric element 302. That is, for example, it is considered that the information regarding the activity amount (exercise amount) of the animal to which the wireless sensor terminal 102 is attached is included. The technique of changing the transmission frequency to reflect the amount of animal activity is a new type of measurement technique that has not existed before.

  The receiving device 104 (see FIG. 1) includes means for determining the number of receptions per unit time of a signal received from a specific wireless sensor terminal 102. In addition, information regarding the number of receptions per unit time can be output in a form as required, such as an image or data. The means having such a function can be realized by software means including a program and a CPU, for example.

  When the program in the memory 404 detects that the voltage at the terminal 408 has changed from Low to High, the CPU 402 may be controlled to obtain temperature information using the temperature sensor 220. For example, if the temperature sensor 220 is just a resistor, the program in the memory 404 controls the CPU 402 to pass a current through the temperature sensor 220 and measure the resistance value in response to detection of a voltage change at the terminal 408. Also good. The program in the memory 404 may control the CPU 402 so that the obtained temperature information is included in the transmission signal.

  The transmission circuit 406 is configured to modulate the transmission data formed by the CPU 402 into a signal for transmission.

  The operation of the transmitter 204 described so far will be summarized using the flowchart of FIG. Step 500 shows activation of the transmitter 204. When the transmitter 204 is activated, when the transmitter 204 is activated, the program in the memory 404 controls the CPU 402 to periodically check the voltage at the terminal 408 (steps 502 and 504). When detecting that the voltage has changed in a predetermined direction, the program in the memory 404 controls the CPU 402 so as to obtain information on the temperature by using the temperature sensor 220 (step 506). In the following step 508, the program in the memory 404 controls the CPU 402 so as to form data for transmission, but the temperature data measured in step 506 is also included in this data for transmission. The data formed in the transmission format is modulated into a transmission signal by the transmission circuit 406 and transmitted through the antenna 206 (step 510). Thereafter, returning to step 502, the program in the memory 404 again controls the CPU 402 to check the voltage at the terminal 408 periodically.

  It should be noted that the above configuration is merely an example of an embodiment of the present invention. For example, steps 502 and 504 described above can be replaced with a configuration in which an interrupt is generated in the CPU 402 when the voltage at the terminal 408 changes. For example, the configuration can be replaced with a so-called CMOS input interrupt circuit. Steps 506 and subsequent steps can be executed in response to the occurrence of the interrupt. According to such an embodiment, the periodic voltage check by the CPU 402 is not necessary, and it is the same as the voltage being monitored with zero power consumption. Therefore, the power consumption can be reduced as compared with the embodiment illustrated in FIG. Can do.

  In the embodiments described so far, the CPU 402 is used to control the operation of the transmitter 204. However, in some embodiments, the voltage check and signal transmission are performed only by a hardware circuit without using the CPU. It can also be configured as follows. In this case, the transmission circuit 406 is configured to transmit a predetermined signal triggered by a change in the voltage at the terminal 408 in a predetermined direction. From the viewpoint of power consumption, it can be said that the embodiment using no CPU is preferable to the embodiment shown in FIGS. 4 and 5 using the CPU.

  By the way, as depicted in FIG. 1, the sensor network system 100 exemplified in this specification includes a plurality of wireless sensor terminals 102 with respect to one receiving device 104. Therefore, the receiving device 104 must distinguish from which transmitter 102 the received data is transmitted. In this embodiment, the baud rate is used for individual identification of the wireless sensor terminal 102. Specifically, each wireless sensor terminal 102 is configured to transmit frames having the same message length and to transmit data at different baud rates.

  For example, consider an example in which an 8-bit telegram is transmitted using FSK (frequency modulation). Assume that one of the wireless sensor terminals 102 transmits at 10000 bps and the other transmits at 1000 bps. Since the baud rate is a time for sending a 1-bit message, a baud rate of 10000 bps means that it takes 100 microseconds to transmit 1-bit data. Then, when an 8-bit telegram is transmitted at a baud rate of 10,000 bps, it can be observed that the electric field strength increases for 800 microseconds at the frequency used for modulation.

  On the other hand, a baud rate of 1000 bps means that it takes 1000 microseconds to transmit 1-bit data. Therefore, when the same data is transmitted at a baud rate of 1000 bps, it is observed that the electric field strength increases for 8000 microseconds at the modulation frequency. The receiving device 104 is configured to recognize such a signal duration (e.g., 800 microseconds or 8000 microseconds), and based on the duration, determines the baud rate of the signal, and based on the determined baud rate, The transmission terminal is configured to be able to perform individual identification.

  The outline of the configuration of the receiving apparatus 104 will be described with reference to FIG. The receiving apparatus 104 includes a receiving antenna 602 for receiving a transmission radio wave and a receiving circuit 604, an A / D conversion circuit 606 for A / D converting the received signal, and an FFT for frequency converting the A / D converted received signal. A circuit 608, a CPU 610, and the like are provided. The receiving device 104 includes at least three storage areas 612 to 616. The first storage area 612 can be used to store a program for causing the CPU 610 to perform a desired function. The second storage area 614 is used to store a database that stores correspondence information that associates a specific individual of the plurality of wireless sensor terminals 102 with a specific baud rate. The third storage area 616 is used for storing received data. The first to third storage areas 612 to 616 can be realized on a physically same storage medium in some embodiments, and are configured by physically different storage media in some embodiments. You can also. The storage medium that can be used as the first to third storage areas 612 to 616 may be any medium as long as it satisfies the requirements of capacity and speed, such as DRAM, SDRAM, flash memory, and hard disk. be able to.

  One aspect of the reception operation of the reception device 104 will be described with reference to FIG.

  Step 700 shows activation of the receiving device 104. When the signal can be received, the receiving apparatus 104 receives the signal by the receiving antenna 602 and the receiving circuit 604, and successively A / D converts it by the A / D converting circuit 606, and a predetermined number of samples are accumulated. Then, it is configured to be converted into frequency data one after another by the FFT circuit 608 (step 702). As will be described later, the receiving circuit 604 is preferably configured to demodulate a signal using a direct conversion method. The program stored in the storage unit 612 controls the CPU 610 so that the data converted by the FFT circuit 608 is sequentially stored in the storage unit 616 (step 704). Therefore, the storage area 616 must have a capacity that can store an amount of frequency data corresponding to multiple FFT processes.

  Under the control of the program in the storage area 612, the CPU 610 checks whether or not frequency data for a predetermined time has been accumulated in the storage area 616 (step 706). If accumulated, the CPU 610 reads out frequency data for a predetermined time from the storage area 616 in accordance with the control of the program (step 708).

  In step 710, the CPU 610 checks the time variation of the frequency power at the modulation frequency used by the wireless sensor terminal 102 according to the program. Therefore, it is assumed that the wireless sensor terminal 102 transmits data using FSK. In addition, the modulation frequency used by the wireless sensor terminal 102 is preferably known in the receiving device 104. If the increase in frequency power at the modulation frequency continues for a certain period or longer, it is determined that the signal is from any one of the plurality of wireless sensor terminals 102, and the process proceeds to the next step 712. If no increase in frequency power is observed at the modulation frequency, it is determined that no signal has been received from the wireless sensor terminal 102 during that period, and the process returns to step 702.

  In step 712, the CPU 610 determines the baud rate of the received signal from the period in which the frequency power is increasing and the message length of the transmission data according to the program. Here, the message length of the transmission data needs to be known in advance by the receiving apparatus 104. In addition, all the wireless sensor terminals 102 that transmit signals to the receiving device 104 need to be configured to perform data transmission with the same message length. That is, as described above, all the wireless sensor terminals 102 that transmit signals to the receiving device 104 are configured to transmit frames of the same message length, and transmit data at different baud rates. It is configured as follows.

  In step 714, the CPU 610 uses the database stored in the second storage area 614 according to the instruction of the program in the storage area 612 and uses the specific wireless sensor corresponding to the specific baud rate determined in the previous step. Terminal 102 is identified. In step 716, the program may cause the CPU 610 to operate so as to store the data identified in step 710 in association with the wireless sensor terminal 102 identified in step 714, for example, in the storage area 616.

  Reference numeral 718 indicates that the process returns to step 702 again. However, the processing of the CPU 610 returns to step 702 is not limited to the illustrated position, and may be, for example, between steps 710 and 712 or between steps 712 and 714. These are appropriately determined depending on the processing capability of the CPU 610 and the program configuration of the storage area 612.

  In some embodiments, the receiving device 104 includes a circuit 622 for forming an image signal, and the CPU 610 and the program read out received data associated with a specific wireless sensor terminal 102 from a predetermined storage area 616, A signal for displaying it may be formed by the image signal forming circuit 622 and output from the image signal output terminal 624.

  Further, in some embodiments, the reception device 104 includes an interface 626 for communicating with an external device by wired or wireless means, and the CPU 610 and the above program send received data to a specific wireless sensor terminal 102. It may be configured to output to an external device in association with. Such an external device may be, for example, a USB memory or another computer.

  It should be noted that the above flow and configuration are merely examples of the embodiment of the present invention. For example, since the sampling frequency of the A / D conversion circuit 606 and the number of samples for which the FFT circuit 608 performs frequency conversion are known, the check process in step 706 described above is omitted, and the storage area 616 is simply given at predetermined time intervals. Steps 706 and 708 can be combined into a configuration in which the frequency data for a predetermined time is read out from.

  As described above, all the wireless sensor terminals 102 that transmit signals to the receiving device 104 are configured to transmit frames of the same message length, and transmit data at different baud rates. It is configured. The receiving device 104 is configured to be able to store the message length in a form usable by the CPU 610 in advance, and the CPU 610 uses information relating a specific baud rate to a specific wireless sensor terminal 102. It is configured so that it can be stored in advance in a possible form. According to such a configuration, the receiving device 104 can perform individual identification of the wireless sensor terminal 102 that has transmitted the data based on the baud rate of the received data.

  Since the receiving device 104 can identify an individual using the baud rate, all the wireless sensor terminals 102 can also use the same modulation frequency. However, in that case, if a plurality of wireless sensor terminals 102 transmit data at the same time, they cannot be separated.

  That is, when a plurality of sensor terminals are configured to communicate at the same frequency, if the plurality of sensor terminals transmit data simultaneously, the transmission signals collide and cannot be distinguished on the receiving device side. However, for the purpose of measuring organisms, the transmission timing of the sensor terminal is also random due to the randomness of the biological activity, and transmission signal collision is less likely to occur. Instead, like the above configuration, it is better to save the power required for transmission by omitting the individual identification information and synchronization information from the communication frame, and to extend the life of the sensor terminal, It is much more profitable for managing and measuring a large number of organisms.

  However, depending on the embodiment, the transmission frequency of the wireless sensor terminal 102 may be different depending on the terminal. In that case, it is preferable that the receiving apparatus 104 stores information such that the transmission frequency can be associated with each terminal in addition to the baud rate. Such information could be data in a very simple format, for example {terminal ID, baud rate, frequency}. The program in the storage area 612 is configured to specify a terminal that has transmitted data from the specified frequency and baud rate using such information.

  Further, as described in relation to step 710, in the above configuration, the data frame and the transmission frequency transmitted from the wireless sensor terminal 102 are specified by analyzing the data read from the storage area 616. Therefore, a hardware circuit for specifying a communication frame and a communication frequency is not necessary, and the receiver can collectively convert the frequency spectrum to a storage area 616 without narrowing down the band of the received signal. Good. Therefore, it is preferable that the receiving device 104 is configured to receive a signal by a direct conversion method.

  In this way, by using the direct conversion method and software radio technology on the receiver side, there is no need to include individual identification information, timing synchronization information / frame synchronization information in the transmission data of the wireless sensor terminal, and the transmission data is reduced to short power. Culture will be able to save the power required for transmission.

  FIG. 8A illustrates a transmission data format often used in wireless communication. One frame 800 of transmission data is roughly divided into five parts: a preamble 802 for clock synchronization, a unique word 804 for frame synchronization, an individual identification information 806, a data portion 808, and an error detection / correction information portion 810. Consists of Of these, a total of 40 bits of 16 bits, 16 bits, and 8 bits are often used for the preamble 802, the unique word 804, and the individual identification information 806, respectively. However, according to the configuration disclosed above in relation to the wireless sensor terminal 102 and the receiving device 104, it is not necessary to include clock synchronization information and frame synchronization information, and it is not necessary to include individual identification information. . According to the disclosed configuration, it is only necessary for the receiving device 104 to be able to determine the start of a frame, so that the 40 bits of the portions 802 to 806 can be replaced with, for example, only 2 bits of frame start information.

  The power required for transmission is almost proportional to the number of bits. Therefore, the fact that 40 bits can be reduced to 2 bits means that the transmission power has been successfully reduced to about 1/20. Of course, in addition to frame start information and the like, the transmission signal includes information to be transmitted (for example, temperature) and error detection information, so the number of bits of the entire frame can be reduced to 1/20. It wasn't done. However, regarding the header portion transmitted prior to the data portion, the number of bits can be reduced to 1/20, and the transmission power can be reduced to approximately 1/20 for that portion.

  FIG. 8B illustrates an example of a frame configuration of a signal transmitted from the wireless sensor terminal 102 to the receiving device 104. In this example, one frame 820 includes a 2-bit preamble 822 for teaching the start of the frame, an 8-bit data portion 824, and a 1-bit parity bit 826 for error detection. In order to reduce the number of bits as much as possible, parity information, which requires only one bit, was adopted for error detection information. As a result, even if 8 bits were used for the data portion, the number of bits per frame could be suppressed to 11 bits. In the example of FIG. 8A, since the number of bits per frame is 60 bits, the number of bits can be reduced by approximately 82%, and transmission power corresponding to the number of bits can be saved. It goes without saying that this claim configuration is merely an example.

  In some embodiments, the wireless sensor terminal 102 includes a temperature sensor 220 as described above. Therefore, the data portion 824 can include temperature information. Information such as the remaining battery capacity may be included.

  In another embodiment, no sensor other than the vibration sensor 202 is mounted on the wireless sensor terminal 102, and the wireless sensor terminal 102 only transmits a signal each time a predetermined charge is accumulated in the capacitor 308. is there. In such an embodiment, there is no particular information to be included in the data portion 824. In that case, the number of bits of the preamble 822 and the data portion may be determined so that the number of bits of the frame 820 becomes a length that enables individual identification by the baud rate in the receiving apparatus 104. In such an embodiment, the bits to be transmitted may simply be a sequence of 0s or 1s.

  As described above, the frequency of a signal received from a certain wireless sensor terminal 102 can be interpreted as including information on the amount of activity of an object to which the wireless sensor terminal 102 is attached. Therefore, the receiving device 104 is configured to output such information. The operation | movement which concerns on such a structure is demonstrated using the flowchart of FIG.

  Step 900 indicates the start of processing. In step 902, the CPU 610 reads out received data stored in association with a specific wireless sensor terminal 102 from the storage area 616 based on control of a program stored in the storage area 612. These received data are stored in step 716 of FIG. In step 716 of FIG. 7, these pieces of received data are stored together with information about the received time as well as information about the wireless sensor terminal 102 that transmitted the received data. Based on the time information, the CPU 610 calculates the number of receptions per unit time according to the above program (step 904). In step 906, the calculated result is shaped into a predetermined format, and in step 908, the shaped data is output. In step 906, the CPU 610 may create data for outputting an image by associating the calculation result with the specific transmitter 102 according to the program. Further, it may be shaped into a format for output to an external memory or an external computer. The output destination in step 908 can be a display device, a printer device, a removable medium such as a USB memory, a wired or wireless network system, and the like.

  By this specification, the new vibration sensor structure illustrated by the code | symbol 202 which has very little power consumption and has even a power generation function was disclosed. By using this vibration sensor, a wireless sensor terminal that is extremely excellent in power saving can be realized. This vibration sensor can be manufactured in an extremely small size by using an existing MEMS manufacturing process or semiconductor manufacturing process, and is advantageous in reducing the size, weight, and cost of the apparatus. In addition, by adopting a new configuration that uses the baud rate for terminal identification and also extracts data from received radio waves offline, it is possible to significantly reduce the number of bits of transmission data and reduce the power required for transmission. Significant savings can be made. Also with this feature, the power saving performance of the wireless sensor terminal can be further improved. Furthermore, since the wireless sensor terminal has a new configuration in which vibration energy is converted into electric energy and stored in the capacitor 308, and a signal is transmitted each time a certain amount of energy is stored, the amount of activity and momentum Can be detected in the form of transmission frequency from the wireless sensor terminal.

  In addition to the above-described embodiments, the present invention can take various embodiments. For example, in some embodiments, the wireless sensor terminal and the receiving device may be configured to be identified based on a difference in modulation frequency. That is, a plurality of wireless sensor terminals are configured to transmit data using radio waves having different frequencies, and information on associating a specific frequency with a specific transmitter (for example, storage) In the area 614, the signal from the wireless sensor terminal that uses the frequency of the measurement as the modulation frequency is identified by examining the change in the power of the specific frequency over a certain period. Also good. Needless to say, both the individual identification based on the frequency and the individual identification based on the baud rate may be used.

  In order to make the circuit as small as possible and to reduce power consumption as much as possible, the wireless sensor terminal 102 is preferably configured so that only a transmitter is mounted and no receiver is mounted.

  The programs that have appeared in the above description can be sold by being stored in a storage medium such as a CD-ROM or USB memory, or can be sold by a technique such as downloading through a network.

  Although examples of embodiments of the present invention have been described using the sensor network system 100, these descriptions and the accompanying drawings are not intended to limit the scope of the present invention, but for a deep understanding of the present invention. It was only provided for the purpose of serving. It goes without saying that the present invention can take various embodiments without departing from the technical idea of the present invention. An example of a preferred embodiment of the present invention is shown in each claim described in the appended claims. However, the present specification includes novel inventions other than the invention specified in the claims. Note that it is disclosed. The scope of the present invention is not limited to the configurations and methods explicitly described in the specification, and includes combinations of various aspects of the present invention disclosed in the present specification. Among the present inventions, the invention to be patented is specified in the appended claims, but the inventor has disclosed the present specification even if the invention is not currently specified in the claims. I would like to remind you that you may claim the invention disclosed in the future in the future.

DESCRIPTION OF SYMBOLS 100 Sensor network system 102 Wireless sensor terminal 104 Receiver 106 Wireless medium 202 Vibration sensor 204 Transmitter 206 Antenna 208 Battery 212 Voltage detection line 214 Power supply line 220 Temperature sensor 302 Piezoelectric element 304,306 Diode 308,328 Capacitor 310,322 CMOS Logic inversion circuit 324 Monostable multivibrator 326 Switch 404 Memory 406 Transmission circuit 602 Reception antenna 604 Reception circuit 606 A / D conversion circuit 608 FFT circuit 610 CPU
612, 614, 616 Storage area 622 Image signal forming circuit 626 Interface

Claims (10)

A piezoelectric element;
A first capacitor connected to the piezoelectric element via an AC / DC converter circuit;
A CMOS logic inversion circuit having an input unit connected to the first capacitor, and configured to change an output voltage in response to a voltage across the first capacitor exceeding a predetermined threshold value. A CMOS logic inversion circuit;
A wireless transmission circuit;
A wireless sensor terminal configured to perform signal transmission by the wireless transmission circuit with a change in output voltage of the CMOS logic inversion circuit as a trigger.   The radio | wireless of Claim 1 further provided with the 2nd capacitor | condenser connected in parallel with the said 1st capacitor | condenser through the switch circuit which turns on for a fixed period according to the change of the output voltage of the said CMOS logic inversion circuit. Sensor terminal.   The wireless sensor terminal according to claim 2, configured to supply power stored in the second capacitor to the wireless transmission circuit.   4. The wireless sensor terminal according to claim 1, wherein the wireless transmission circuit is configured to include information on a temperature or a remaining battery level in a communication frame to be transmitted. 5.   The wireless sensor terminal according to any one of claims 1 to 4, wherein the wireless transmission circuit is configured not to include individual identification information and / or synchronization information in a communication frame to be transmitted. A receiving device comprising a receiving circuit capable of receiving a signal transmitted from the wireless sensor terminal according to any one of claims 1 to 5,
Wherein in order to the wireless sensor terminal to obtain the information about the amount of activity organism mounted, further comprising means for determining the reception count per unit time of a signal received from the wireless sensor terminal, the receiving apparatus. A sensor network system including the wireless sensor terminal according to claim 1 and the receiving device according to claim 6 . An operation method of an apparatus for creating information on an activity amount of a living individual,
Receiving a signal transmitted from a wireless sensor terminal attached to the living individual, wherein the wireless sensor terminal is a terminal that emits a wireless signal each time an accumulated amount of energy generated by vibration reaches a predetermined value; The receiving step;
Configuring information relating to the amount of activity of an individual organism to which the wireless sensor terminal is attached based on the number of receptions per unit time of a signal emitted from the wireless sensor terminal;
Including a method. A piezoelectric element;
A first capacitor connected to the piezoelectric element via an AC / DC converter circuit;
A CMOS logic inversion circuit having an input unit connected to the first capacitor, and configured to change an output voltage in response to a voltage across the first capacitor exceeding a predetermined threshold value. A CMOS logic inversion circuit;
A vibration sensor. 10. The vibration according to claim 9 , further comprising a second capacitor connected in parallel to the first capacitor via a switch circuit that is turned on for a certain period in response to a change in an output voltage of the CMOS logic inversion circuit. Sensor.

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